Not applicable.
The present invention relates to a metering pump device, particularly for a heating appliance, comprising a pump arrangement for the delivery to an outlet region of liquid which can be supplied through an inlet region, and also a valve arrangement by means of which the pump arrangement can be selectively connected to the inlet region to receive liquid, or connected to the outlet region to deliver liquid.
From German Patent Document DE 198 60 573 A1 a metering pump device is known in which a pump piston acting as a pumping member and also two respective valve sliders forming valve elements are displaceable by a magnet coil against the force of respective prestressing springs. In order to attain the required synchronization of movement of the different components which can be displaced by the single magnet coil in order to carry out inlet or outlet working cycles, their inertial masses and the prestress forces of the respectively allocated prestressing springs have to be exactly matched to each other. This necessitates compromises in the design of different components, or requires a comparatively complicated structure, with the consequence that the exact matching of the different courses of motion to each other can become lost under the influence of external circumstances, such as e.g. the temperature of the overall system, and thus this metering pump device cannot operate in a satisfactory manner.
From European Patent Document EP 0 930 434 A2 a metering pump device is known in which both a pump piston and also a valve slider of a relief valve can be moved by a single magnet coil. Further valve sliders or valve elements are present which are displaceable between a shutoff position and a release position according to the liquid pressure, for changing over between receiving or delivery working cycles. Here also it is necessary for the different system components, or also the forces provided by prestressing springs, to correspond exactly to the existing liquid supply pressure in order to attain a correct manner of operation.
The present invention has as its object to provide a metering pump device that with a comparatively simple structure ensures reliable functioning.
According to the invention, this object is attained by a metering pump device, particularly for a heating appliance, comprising a pump arrangement for the delivery of liquid which can be supplied via an inlet region to an outlet region, and also a valve arrangement by means of which the pump arrangement can selectively be brought into connection with the inlet region to receive liquid, or be brought into connection with the outlet region for the delivery of liquid.
It is further provided that the valve arrangement comprises a valve member which can be brought into a first actuating position and into a second actuating position, where in the first actuating position the valve member permits a liquid supply from the inlet region to the pump arrangement and prevents a liquid delivery from the pump arrangement to the outlet region, and in the second actuating position the valve member prevents a liquid supply from the inlet region to the pump arrangement and permits a liquid delivery from the pump arrangement to the outlet region.
The metering pump device according to the invention is thus basically divided into two mutually independent system regions, namely first, the pump arrangement by means of which liquid can be received from an inlet region and delivered to an outlet region, and also the valve arrangement which selectively brings the pump arrangement into connection with the inlet region or the outlet region for liquid exchange. These two system regions can be operated independently of each other and of course are consistent with each other in their different displacement or actuating movements without however requiring a positive mechanical coupling. This simplifies the structure of the metering pump device according to the invention in comparison with the devices known from the prior art.
For example, according to the present invention it can be provided that the pump arrangement comprises a piston displaceable in a pump chamber, and that the pump chamber can be selectively brought by the valve arrangement into connection with the inlet region or the outlet region.
The valve member is displaceable between the first actuating position and the second actuating position and can, for example, be constituted such that for the production of fluid exchange connections it has a channel region by means of which the pump arrangement can be brought into liquid exchange connection with the inlet region and/or the outlet region. It can furthermore be provided that the valve member is displaceable between the first actuating position and the second actuating position.
In an embodiment which is simple to construct and which operates reliably, it can be provided that the valve member is translatable for displacement between the first actuating position and the second actuating position. Alternatively or additionally to this translational movement of the valve member, the changeover between different actuating positions can also be attained in that the valve member is rotatable for displacement between the first actuating position and the second actuating position.
According to an aspect, the metering pump device according to the invention is characterized by a first actuating force producing arrangement for the production of a valve actuating force for the valve member and also a second actuating force producing arrangement for the production of a pump actuating force for the pump arrangement substantially independently of the production of the valve actuating force. A positive motion coupling of the different system regions, pump arrangement and valve arrangement, is thus not provided, with the consequence that the different system regions can be controlled, even in conformity with different operating states, for example flow speeds, affected by viscosity, of the liquid to be delivered.
It can, for example, be provided that the first actuating force producing arrangement and/or the second actuating force producing arrangement are constituted for the production of a magnetic force interaction.
An embodiment that uses the available constructional space can be attained in that the pump piston is displaceable in a piston displacement direction in the pump chamber and that the valve member is arranged in the pump arrangement in the piston displacement direction.
In order to be able to attain a quasi-continuous liquid delivery from the metering pump device according to the invention, a liquid reservoir can be provided in the flow region between the pump arrangement and an outlet aperture of the outlet region. The outlet aperture of the outlet region can then be closed by the valve member, or by a closure member motion-coupled to it.
According to a further aspect, the present invention provides for a valve arrangement which can be used in an application in connection with a metering pump device according to the invention. In this valve arrangement, a valve member is provided which can be brought by rotary motion into plural actuating positions. The rotation of a valve member for changing over between different actuating positions leads to a comparatively small constructional size of a valve arrangement, since no constructional space has to be kept in readiness for an element which is to be displaced linearly.
For example, it can be provided that an armature element is securely coupled to rotate with the valve member, and that the armature element is arranged for magnetic force interaction with pole elements of a magnet coil arrangement. In order to keep the construction and also the drive cost as low as possible, it is proposed that the valve member is prestressed into one of the actuating positions by a prestressing arrangement, preferably a torsion spring.
It can furthermore be provided that a channel arrangement is provided in the valve member, a first channel end region of the channel arrangement being connected to a first valve opening, and a second channel end region of the channel arrangement being able to be brought selectively, by rotation of the valve member, into connection with a second valve opening or a third valve opening.